To define the role of taurine in the heart we propose: I) to deplete the heart of taurine, determine what functional changes follow, then supply taurine in an attempt to restore function to normal; II) to determine what effects on heart function follow raising heart taurine levels above normal; III) to study taurine distribution in the normal and hypertrophied left ventricle of dogs with particular attention to the transmural taurine gradients and the base-to-apex gradients; and IV) to extend these studies to disease models in rats. We have found it possible to lower taurine levels in the hearts of rats and mice by giving high doses of beta alanine (a carboxylic acid analogue of taurine) and of glucose. We will try to confirm in rats (and mice) the report that potassium deficient diets also lower taurine. To determine heart function we plan to use oscillographic and pen-writing EKG equipment and to use electrolytes like BaC12 and CaC12 to induce arrhythmias. The effects of producing supranormal heart taurine levels by giving high doses of taurine or mercaptoethylamine will also be studied. Since taurine is a naturally occurring anti-arrhythmic principle concentrated in the heart, its role in heart function should be investigated to determine its potential therapeutic usefulness.